Ctactile

Ctactile, commonly referred to as C-tactile (CT) afferents, denotes a class of unmyelinated nerve fibers found primarily in hairy skin that respond preferentially to gentle, slow stroking. These fibers are thought to mediate the affective or emotional dimension of touch, in contrast to the discriminative sense carried by faster, myelinated mechanoreceptors.

CT afferents have small peripheral receptive fields and respond best to brush-like stimulation at moderate velocities, typically around 1 to 10 centimeters per second, with peak pleasantness reported near about 3 cm/s. They show little response to high-velocity stimulation and are distinct from Aβ mechanoreceptors that convey fine tactile details. The conduction velocity of CT fibers is slow, reflecting their unmyelinated nature.

Neural pathways for CT signals project from the skin to the spinal cord and ascend to higher brain regions, with prominent involvement of the posterior insular cortex. From there, CT signaling is integrated with limbic and reward networks, aligning tactile input with affect, emotion, and social context. This neural routing underpins the proposed role of CT touch in social bonding, mood modulation, and stress regulation. Additionally, CT activity may contribute to pain modulation and relaxation responses.

Distribution and development: CT afferents are most robust in hairy skin and are less prevalent in glabrous (hairless) skin. They have been described in humans and observed in several mammalian species, reinforcing their proposed evolutionary role in social touch.

Clinical relevance: research investigates CT function in conditions characterized by altered social touch processing, such as autism spectrum disorders and mood disorders, though findings are still evolving.